The application generally relates to electrical connections for compressors. The application relates more specifically to providing electrical connections through the shell or housing of a hermetic compressor.
FIG. 1 shows a top, partial cross-sectional view of a prior art compressor 100. The compressor 100 has a shell 110 that provides a hermetically sealed environment for electrical and mechanical components inside the shell 110. To maintain proper operation of the compressor 100, the integrity of the hermetically sealed environment cannot be breached by the electrical connections through the shell 110. Further, when a flammable refrigerant is used in the compressor 100 as the working fluid, any sparking or arcing inside the compressor 100 should be avoided.
One type of electrical connection into the hermetically sealed environment of the shell 110 can be provided by a power terminal 112. The power terminal 112 has to maintain the hermetically sealed environment while withstanding the harsh operating conditions associated with the compressor 100. The power terminal 112 can be located within an aperture in the shell 110. The power terminal 112 can have a cup-shaped metal collar 126 with a bottom wall. The bottom wall has holes that permit conductor pins 128 to pass through to provide the electrical connection through the shell 110. The collar 126 is sealed in the shell aperture by welding and the pins 128 are sealed within the collar 126 by fused glass insulation. To further stabilize the terminal 112, the fused glass insulation surrounding the pins 128 can be covered with epoxy or shielded by ceramic collars.
A fence 130 can surround and protect the power terminal 112. A molded plug (not shown) can be configured to couple with the fence 130 and, thereby, make an electrical connection with the pins 128 outside the shell 110. To accomplish this connection on the outside of the shell, the pins 128 can be provided with a tab (not shown). For example, each pin 128 may include an attached, e.g., welded, 0.250 inch tab that can connect to a 0.250 inch spade connector crimped onto the end of a voltage supply wire or conductor. Any of the previously described connections, e.g., pin-tab, tab-connector, connector-wire, can become corroded or loose and result in arcing or sparking that can ignite the surrounding atmosphere if the compressor 100 is located in a hazardous or explosive environment, such as grain silos with grain dust, areas with gasoline vapors, mines, etc.
In addition, the power terminal 112 relies on through air and/or over surface clearance to insulate the terminal pins both line to line and each line to ground, where the shell 110 and/or collar or terminal body 126 are at earth ground potential. Even if the connections and insulation are sound, there can be multiple ways for an arc or spark to occur at the terminal pins 128 when the pins 128 are energized. For example, a conductive atmosphere (e.g., contaminants and/or moisture) could reduce the dielectric (insulation properties) between pins 128 and bridge the voltage. Another example is that an excessive grid voltage could produce corona or other micro conductivity that could also reduce the dielectric between pins 128. A further example is that insects or small wildlife can bridge the voltage between pins 128. A service person may also inadvertently bridge the voltage between pins 128 with tools or other items while performing maintenance with the terminal cover removed.
Plugs, tabs, connectors or wires similar to those used on the outer ends of the pins 128 can be used on the inside end of the pins 128 to accomplish the electrical connection between the electrical components inside the shell 110 and the power terminal 112. When using a flammable refrigerant, the connection(s) at the inner end of the pins 128 should not generate a spark or arc due to the risk of fire or explosion inside the shell 110.
There can be problems associated with the use of sealed glass pin power terminals 112. The terminals 112 require extensive tooling that is costly and not easily modified to add or subtract pins 128 if additional or fewer electrical connections are required. The prefabrication process is costly, complex and time consuming. Further, as the terminals 112 are being welded to the shell 110, the glass seals can be damaged and, thus, the assembly must be discarded and replaced. The replacement of the assembly can be quite costly as significant time and expense has already been invested in pre-assembling the power terminal 112. Even worse, the damaged glass seals may go undetected, resulting in an eventual compressor failure. Further, the plug and the corresponding electrical connections may become loose resulting in a compressor failure. The additional parts and complexity needed to connect to the pins 128 can add cost and create additional junctions that may fail.
Therefore, what is needed is an electrical connection through the shell of a hermetic compressor that can be easily assembled and installed and that reduces the possibility of sparking or arcing inside or outside of the compressor shell.